Overview

Nitric acid (HNO₃) is a powerful strong acid and an even more powerful oxidizer. It is consumed in enormous volume for fertilizer (ammonium nitrate, urea-nitrate), metal surface treatment (stainless passivation, brass etching), explosives manufacture, and specialty chemical synthesis. Unlike most industrial chemistries where the stored concentration is narrow (e.g., 37% HCl, 50% NaOH), commercial nitric ships across a wide concentration range — and the correct tank material is entirely concentration-dependent.

The Concentration Tiers — Enduraplas Data

Polyethylene compatibility with nitric acid changes dramatically with concentration. The following ratings are from Enduraplas / Equistar published polyethylene compatibility data:

Why Oxidizing Acids Are Different

Most acid chemistries on polyethylene compatibility charts attack the resin by acid-catalyzed hydrolysis — a slow, temperature-dependent process. Nitric acid at high concentration attacks polyethylene by oxidative chain scission: the acid oxidizes the carbon-carbon backbone of the polymer directly. This is orders of magnitude faster than hydrolytic attack, and it accelerates sharply with both concentration and temperature. The compatibility cliff between 70% (limited service) and 98% (immediate failure) is not gradual — it's a step change.

What to Use Instead (for >70%)

For nitric concentrations above the polyethylene rating window, industry-standard tank materials are:

• 316L stainless steel — the workhorse for 50–95% nitric. 316L (not 304) because the molybdenum content resists pitting. Nitric passivates stainless, so the oxide layer is actually strengthened by routine exposure.
• Glass-lined steel — for 95–98% fuming nitric. Glass-lined tanks (Pfaudler, De Dietrich) are the standard for pharmaceutical and specialty-chemical nitric service.
• PTFE (Teflon) lined carbon steel — for mixed acid (sulfuric + nitric) service where neither stainless nor glass is ideal.
• Tantalum or high-nickel alloys — for elevated-temperature nitric or nitric-HF mixtures.

None of these are polyethylene. If you came to this page expecting to buy a polyethylene tank for concentrated nitric, the honest answer is: we don't sell the right product for that service, and neither does any other rotomolded-tank manufacturer.

Dilute Nitric (≤30%) — Polyethylene Works

At concentrations up to 30%, polyethylene (both HDPE and XLPE) provides reliable service at both ambient and elevated temperature. Typical applications at this concentration: metal-surface brightening, laboratory-grade dilute nitric, agricultural fertilizer intermediates. Standard industrial MOC stack works:

• HDLPE or XLPE at 1.9 ASTM design specific gravity
• Viton gaskets (EPDM fails in oxidizing acid)
• Hastelloy C-276 or Titanium bolting
• CPVC or PVDF fittings (PVC is marginal above room temperature)

This is the same MOC stack as for sulfuric acid at comparable concentrations. If you have an existing sulfuric tank setup, dilute nitric is likely compatible with the same hardware.

Mid-Concentration (30-70%) — Limited Service

Between 30% and 70% concentration, Enduraplas rates polyethylene as Limited (O) at 140°F service temperature. In practice this means:

• Ambient-temperature storage is acceptable.
• Heated storage (process loops, heat-traced in cold climates) is NOT recommended.
• Tank service life will be measurably shorter than in benign chemistries.
• Budget for tank replacement on a 7–10 year cycle rather than the typical 15–20 year polyethylene service life.

Ventilation — NOx Fumes

All concentrations of nitric acid generate nitrogen oxide (NOx) fumes that are visible (orange/brown) at concentrations above 50% and detectable by odor at much lower concentrations. Tank venting for nitric service must:

• Route vent gases away from occupied work areas.
• Consider scrubbing before atmospheric release — NOx is an OSHA regulated air contaminant.
• Account for oxidizer atmosphere near the vent — no combustibles in the vent path.

Concentration-Band Compatibility (Enduraplas / Equistar Data)

Polyethylene chemical resistance by concentration and service temperature. Satisfactory (S) = long-term service. Limited (O) = occasional only. Unsatisfactory (U) = do not use.

Frequently Asked Questions

Can I store 68% "concentrated" nitric in a polyethylene tank?

Technically within the Enduraplas rating window but at the edge. 68% nitric is an oxidizing and corrosive chemistry that dramatically shortens polyethylene service life. Order a tank commissioned specifically for nitric service, expect 5-10 year replacement cycle, and plan hardware accordingly. For 95%+ nitric, switch to stainless steel.

What's the difference between red fuming nitric (RFNA) and white fuming nitric (WFNA)?

Both are ≥95% concentration. WFNA is 98%+ pure HNO3; RFNA includes dissolved N2O4 that gives it the red-brown color and enhanced oxidizing power. Both exceed polyethylene's rated window. Use stainless or glass-lined steel.

Can I use the same tank for nitric acid and sulfuric acid?

Physically possible at dilute concentrations (under 30%) with HDLPE + Viton + Hastelloy. Do NOT use the same tank for MIXED acid (sulfuric + nitric combined) — mixed acid is an even more aggressive oxidizer and requires PTFE-lined steel.

Does my insurance cover a nitric acid tank leak?

General-liability policies typically exclude concentrated oxidizer releases. Check with your insurance broker; most commercial nitric installations carry a separate chemical-release rider or are covered under a site-specific pollution policy.

Can I convert a used water tank to nitric service?

No, for two reasons: (1) trace organic contamination in a used tank can cause violent reactions with nitric acid; (2) water-tank MOC (EPDM gaskets, standard plumbing) is incompatible. Order a dedicated nitric-service tank from new.

Source Citations

• Snyder Industries — Chemical Resistance Recommendations (current edition)
• Enduraplas / Equistar Technical Tip — Chemical Resistance of Polyethylene (12-page reference)